module.exports = function(m){
  const d = new Date();
  const year = d.getFullYear();
  const month = m || (d.getMonth() + 1);
  let end = 30;
  switch(month-0){
    case 1:
    case 3:
    case 5:
    case 7:
    case 8:
    case 10:
    case 12:
      end = 31;break;
    case 4:
    case 6:
    case 9:
    case 11:
      end = 30;break;
    case 2:
      if( year%4===0 && year%100!==0 || year%400 === 0 ){
        end = 29;
      }else{
        end = 28;
      }
  }
  return [ year + "/" + month + "/" + 1, year + "/" + month + "/" + end ];
}